Crosslinkable graft polymer non preferentially wetted by polystyrene and polyethylene oxide

ABSTRACT

Methods for fabricating a random graft PS-r-PEO copolymer and its use as a neutral wetting layer in the fabrication of sublithographic, nanoscale arrays of elements including openings and linear microchannels utilizing self-assembling block copolymers, and films and devices formed from these methods are provided. In some embodiments, the films can be used as a template or mask to etch openings in an underlying material layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/324,216, filed Dec. 13, 2011, pending, which is a divisional of U.S.patent application Ser. No. 11/765,232, filed Jun. 19, 2007, now U.S.Pat. No. 8,080,615, issued Dec. 20, 2011, the disclosure of each ofwhich is hereby incorporated herein by this reference in its entirety.

TECHNICAL FIELD

Embodiments of the invention relate to methods of fabricating nanoscalearrays of micro-vias, microchannels and microstructures by use of thinfilms of self-assembling block copolymers, and devices resulting fromthose methods, including methods and materials for producing neutralwetting surfaces for use in such methods.

BACKGROUND OF THE INVENTION

As the development of nanoscale mechanical, electrical, chemical andbiological devices and systems increases, new processes and materialsare needed to fabricate nanoscale devices and components. Conventionaloptical lithographic processing methods are not able to accommodatefabrication of structures and features much below the 100 nm level. Theuse of self assembling diblock copolymers presents another route topatterning at nanometer dimensions. Diblock copolymer filmsspontaneously assemble into periodic structures by microphase separationof the constituent polymer blocks after annealing, for example bythermal annealing above the glass transition temperature of the polymeror by solvent annealing, forming ordered domains at nanometer-scaledimensions. Following self assembly, one block of the copolymer can beselectively removed and the remaining patterned film used as an etchmask for patterning nanosized features into the underlying substrate.Since the domain sizes and periods (L_(o)) involved in this method aredetermined by the chain length of a block copolymer (MW), resolution canexceed other techniques such as conventional photolithography, while thecost of the technique is far less than electron beam lithography or EUVphotolithography, which have comparable resolution.

The film morphology, including the size and shape of themicrophase-separated domains, can be controlled by the molecular weightand volume fraction of the AB blocks of a diblock copolymer to producelamellar, cylindrical, or spherical morphologies, among others. Anotherimportant factor in the film morphology is the affinity between thediblock copolymer and the underlying surface.

Preferential wetting interfaces tend to direct the morphology of theself-assembled film. Most surfaces have some degree of preferentialwetting causing the copolymer material to assemble into lines that areparallel to the surface. However, in some applications, it is desirableto produce structures that are perpendicular to a surface, requiring aneutral wetting surface (equal affinity for both blocks (AB) of theblock copolymer to allow both blocks of the copolymer material to wetthe surface, and using entropic forces to drive both blocks to wet theneutral wetting surface. However, neutral wetting surfaces arerelatively uncommon and often require that the surface of the materiallayer to be modified to provide a neutral wetting interface.

Neutral wetting surfaces on silicon oxide (SiO_(x)) or silicon nitride(SiN) have been provided by applying a neutral wetting polymer, which isfabricated by adjusting the amount of one monomer to the other, and iswetting to both blocks of a self-assembling (SA) block copolymer. Forexample, in the use of a diblock copolymer composed of PS-b-PMMA, aPS-r-PMMA random copolymer (60% PS) (which exhibits non-preferential orneutral wetting toward both PS and PMMA blocks and includes across-linkable element) has been cast as a film onto SiO_(x) andcross-linked using UV radiation or thermal processing to form aneutral-wetting mat that loses solubility and adheres to the surface butis not chemically-bound or grafted to the surface.

Additional issues arise in the use of cylindrical-phase PS-b-PMMA blockcopolymers to form self-assembled films whereby, under a typical anneal(at about 180-190° C.), both PS and PMMA blocks wet the air-interface toproduce lines of air-exposed half-cylinders that do not completelyextend to the underlying substrate. Upon removal of the half-cylinderpolymer block (e.g., PMMA) to form an etch mask or template, theunderlying polymer matrix (e.g., of PS) must then be etched to exposethe underlying substrate to be etched.

A prospective alternate material for forming a self-assembling polymerfilm is poly(styrene-b-ethylene oxide) (PS-b-PEO) diblock copolymers,which have been shown to be less defect tolerant (i.e., form largercrystalline grains) than PS-b-PMMA with better ordering.Cylinder-forming PS-b-PEO diblock copolymer materials have been used toproduce perpendicular oriented and highly ordered, hexagonallyclose-pitched cylinders that orient perpendicular to surfaces viasolvent annealing of the copolymer layer. Solvent annealing causedinitial domain segregation at the film-air interface with both polymerblocks wetting the air interface, which was driven downward toward theunderlying substrate as the solvent evaporated and the film dried.

However, because the substrate interface is somewhat preferentialwetting, a layer of the minority polymer block is formed over thesubstrate, which prevents the polymer domains from completely extendingfrom the film-air interface to the substrate itself. In addition, theuse of solvent annealing to form either perpendicular cylinders orparallel lamella produces the same structure universally over thesubstrate, which is undesirable in many applications.

It would be useful to provide a method and system for formingself-assembling polymer films such as PS-b-PEO that overcome existingproblems.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described below with reference to thefollowing accompanying drawings, which are for illustrative purposesonly. Throughout the following views, the reference numerals will beused in the drawings, and the same reference numerals will be usedthroughout the several views and in the description to indicate same orlike parts.

FIG. 1 is a diagram illustrating the reaction for preparing a randomcopolymer according to an embodiment of the present disclosure.

FIG. 2 illustrates a diagrammatic top plan view of a portion of asubstrate at a preliminary processing stage according to an embodimentof the present disclosure, showing the substrate with trenches. FIG. 2Ais an elevational, cross-sectional view of the substrate depicted inFIG. 2 taken along line 2A-2A. FIG. 2B is an elevational,cross-sectional view of the substrate depicted in FIG. 2 in anotherembodiment, taken along line 2B-2B.

FIGS. 3-5 illustrate diagrammatic top plan views of the substrate ofFIG. 2 at various stages of the fabrication of a self-assembled blockcopolymer film according to an embodiment of the present disclosure.FIGS. 3A-5A illustrate elevational, cross-sectional views of embodimentsof a portion of the substrate depicted in FIGS. 3-5 taken, respectively,along line 3A-3A to line 5A-5A. FIG. 5B is a view of a portion of FIG.5A in a subsequent processing step.

FIG. 6 illustrates a diagrammatic top plan view of a portion of asubstrate at a processing stage according to another embodiment of thepresent disclosure in the fabrication of a self-assembled blockcopolymer film utilizing a cylindrical-phase block copolymer. FIG. 6A isan elevational, cross-sectional view of the substrate depicted in FIG. 6taken along line 6A-6A.

FIGS. 7 and 8 illustrate top plan views of the substrate of FIG. 6 at asubsequent processing stage according to embodiments of the disclosure.FIGS. 7A and 8A illustrate elevational, cross-sectional views of thesubstrate depicted in FIGS. 7 and 8 taken, respectively, along lines7A-7A and 8A-8A. FIGS. 7B and 8B are views of FIGS. 7A and 8A,respectively, in a subsequent processing stage.

FIG. 9 illustrates a diagrammatic top plan view of a portion of asubstrate at a processing stage according to another embodiment of thepresent disclosure in the fabrication of a self-assembled blockcopolymer film utilizing a cylindrical-phase block copolymer. FIG. 9A isan elevational, cross-sectional view of the substrate depicted in FIG. 9taken along line 9A-9A.

FIGS. 10 and 11 illustrate top plan views of the substrate of FIG. 6 ata subsequent processing stage according to embodiments of thedisclosure. FIGS. 10A and 11A illustrate elevational, cross-sectionalviews of the substrate depicted in FIGS. 10 and 11 taken, respectively,along lines 10A-10A and 11A-11A. FIGS. 10B and 11B are views of FIGS.10A and 11A, respectively, in a subsequent processing stage.

FIG. 12 illustrates a diagrammatic top plan view of a portion of asubstrate at a preliminary processing stage according to anotherembodiment of the disclosure, showing patterning of the neutral wettinglayer. FIG. 12A is an elevational, cross-sectional view of the substratedepicted in FIG. 12 taken along line 12A-12A.

FIGS. 13-18 illustrate diagrammatic top plan views of the substrate ofFIG. 12 at subsequent processing stages. FIGS. 13A-18A illustrateelevational, cross-sectional views of embodiments of a portion of thesubstrate depicted in FIGS. 13-18 taken, respectively, along line13A-13A to line 18A-18A. FIGS. 15B, 17B, and 18B are elevational,cross-sectional views of the substrate of FIGS. 15, 17 and 18 takenalong lines 15B-15B, 17B-17B and 18B-18B, respectively.

FIGS. 19A and 19B are cross-sectional views of the substrate depicted inFIGS. 18A and 18B, at a subsequent processing step according to anembodiment of the invention. FIG. 20 is a top plan view of the substrateof FIGS. 19A and 19B in a subsequent processing step. FIGS. 20A and 20Bare cross-sectional views of the substrate illustrated in FIG. 20, takenalong lines 20A-20A and 20B-20B, respectively.

FIG. 21 is a top plan view of the substrate of FIG. 18 at subsequentprocessing stage according to another embodiment of the invention. FIGS.21A and 21B are cross-sectional views of the substrate shown in FIG. 21,taken along lines 21A-21A and 21B-21B, respectively.

FIG. 22 is a top plan view of the substrate of FIG. 21 in a subsequentprocessing step. FIGS. 22A and 22B are cross-sectional views of thesubstrate illustrated in FIG. 22, taken along lines 22A-22A and 22B-22B,respectively.

DETAILED DESCRIPTION OF THE INVENTION

The following description with reference to the drawings providesillustrative examples of devices and methods according to embodiments ofthe invention. Such description is for illustrative purposes only andnot for purposes of limiting the same.

In the context of the current application, the term “semiconductorsubstrate” or “semiconductive substrate” or “semiconductive waferfragment” or “wafer fragment” or “wafer” will be understood to mean anyconstruction comprising semiconductor material, including but notlimited to bulk semiconductive materials such as a semiconductor wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure including, but not limited to, the semiconductive substrates,wafer fragments or wafers described above.

“L_(o)” is the inherent pitch (bulk period or repeat unit) of structuresthat self assemble upon annealing from a self-assembling (SA) blockcopolymer or a blend of a block copolymer with one or more of itsconstituent homopolymers.

Steps in a method for synthesizing a crosslinkable graft polymer that isneutrally wetting to polystyrene (PS) and poly(ethylene oxide) (PEO)according to an embodiment of the invention are illustrated in FIG. 1.The resulting random copolymer can be used, for example, to form across-linked, insoluble polymer mat that is neutral wetting to apolystyrene/poly(ethylene oxide) block copolymer (PS-b-PEO) forfabricating polymer films composed of ordered domains of theself-assembled polymer blocks.

The random graft copolymer of the invention can be prepared by firstpolymerizing para-chloromethylstyrene and styrene monomers together toform a random copolymer. In some embodiments, p-chloromethylstyrenecomprises the majority (y>50%) of the monomers by weight. In otherembodiments, no polystyrene is employed and only p-chloromethylstyrenemonomer is used (y=100%), wherein the resultant polymer is ap-chloromethylstyrene homopolymer.

The random copolymer of the invention can be produced, for example, by afree-radical polymerization reaction. Free-radical polymerization iswell-known in the art and generally has three stages: initiation,propagation, and termination. Initiation is the formation of an activecenter (free radical) and generally requires the use of a free-radicalinitiator. A common type of free-radical initiator is a molecule such asa peroxide (e.g., benzoyl peroxide) or 2,2′-azo-bis-isobutyrylnitrile(AlBN), which decomposes into two or more separate free radicals. Thefree radical reacts with the vinyl group of a monomer to form a newmolecule with the active center on the β-carbon of the former vinylgroup. The active center of the new molecule can then react with aseries of other monomer molecules in the propagation stage to form agrowing polymer chain. The polymerization terminates when two activecenters react with each other to form a polymer inactivated to furthermonomer addition.

Other reactions can, and usually do, occur during the propagation stage.Chief among these reactions are branching, which occurs when the freeradical reacts with the middle of a polymer chain to form a side chain,and scission, which occurs when a polymer chain breaks into two or moreseparate chains. As a result of the random nature of the terminationreactions, as well as the branching and scission reactions, the polymerchains fawned by a free radical reaction can vary widely in length andweight. This variation of polymer chains is characterized by a broadmolecular weight distribution (MWD), also known as polydispersity, whichis defined as the ratio of the weight average molecular weight (M_(w))to the number average molecular weight (M_(n)), or M_(w)/M_(n).Frequently, free-radical polymerization produces polymers with an MWD of3 or more.

In some embodiments, the random copolymer of the invention can also beproduced by a controlled/“living” polymerization. In contrast tofree-radical polymerization, living polymers tend to have a lowpolydispersity (MWD). Living polymers are produced by a reversiblepolymerization reaction that has no termination step. Instead, thepolymer and the monomer reach an equilibrium between monomer additionand monomer deletion reactions. Living polymerization processes include,for example, reversible addition fragmentation chain transfer (RAFT)polymerization processes, nitroxide mediated polymerization (NMP)processes, and atom transfer radical polymerization (ATRP) processes.

A RAFT process is a degenerative chain transfer process based onfree-radical polymerization. RAFT agents frequently containthiocarbonyl-thio groups. The polymeric radicals and other radicalsreact with the C═S bond leading to the formation of transient,stabilized radical intermediates. An NMP process, also known asstable-free radical mediated polymerization (SFRP), is another freeradical polymerization using a 2,2,6,6-tetramethylpiperidinyloxy (TEMPO)derivative as the initiator, as further described below. An ATRP processis based on the use of radical polymerization to convert monomers topolymers using an initiator (e.g., an alkyl halide), a catalyst (e.g., atransition metal such as iron or copper complexed by one or moreligands) and a deactivator.

FIG. 1 illustrates an embodiment of a method for producing the randomcopolymer using a “living” polymer reaction. As depicted, initially areaction mixture can be formed by combining the monomerspara-chloromethylstyrene and styrene (when present) with apolymerization initiator. In some embodiments, the initiator is1-[TEMPO]ethyl benzene, which will reversibly form TEMPO and an ethylbenzene radical upon heating. The ethyl benzene radical will react withthe monomers to sequentially insert the monomers. The polymer chain (I)is reversibly terminated with a TEMPO group at its reactive end when inits non-reactive state. Although not shown, the TEMPO-terminatedcopolymer (I) is in equilibrium with free TEMPO and non-TEMPO-terminatedcopolymer.

The copolymer (I) can be prepared using a solution polymerizationprocess or bulk polymerization conditions. In a solution polymerization,the monomers and initiator can be dissolved in a suitable solvent suchas toluene. Examples of other potential solvents include, withoutlimitation, xylene, acetylene, propylene glycol, methyl ether, methylacetate and the like. In a bulk polymerization, the monomers themselvesare the reaction solvent, and the reaction can be carried out atatmospheric pressure and moderate temperatures, e.g., about 70° C.Higher or lower pressures and temperatures can be used; such reactionconditions are considered within the scope of this invention.

The copolymer (I) itself precipitates out of the solution by adding thereaction solution to a “poor” solvent such as methanol, allowing easyrecovery of the polymer (I). If desired, the recovered copolymer (I) canbe washed and dried. The copolymer (I) can then be re-dissolved prior tothe grafting reaction.

The resulting copolymer (I) can be reacted with one or more oligomers orpolymers of poly(ethylene oxide) (PEO) as shown in FIG. 1, where R is ahydrogen or alkyl group. In some embodiments, the PEO is prepared suchthat only one end of the poly(ethylene oxide) is nucleophilic. Anexample of a suitable reagent is monomethoxy poly(ethylene glycol)(MPEG) made reactive by deprotonation of the lone hydroxyl group.

In FIG. 1, the subscripts m and y refer to the number fraction ofreactants styrene and p-chloromethylstyrene, respectively, based on thetotal number of all such reactants that are incorporated into thepolymer, i.e., where m+y=100%. The subscript z is the number fraction ofthe total number of mers that are grafted with PEO. The amount Z of PEOoligomers or polymer chains used in the grafting reaction is selectedsuch that the resulting material can be cast to provide a surface thatis neutral, or non-preferential, wetting to both polystyrene (PS) and toPEO, e.g., both PS and PEO have identical interfacial energies on a filmof the polymer material. The hydroxyl group of the ethylene oxideoligomer/polymer reacts to displace the chlorine atom from thechloromethyl group of the polymer with units derived fromp-chloromethylstyrene to form a graft polymer (II). In particular, theamount of PEO oligomers/polymers chains is selected to be less than thenumber of chlorine atoms available on the chloromethyl moieties. Assuch, some chlorine atoms will remain on the graft polymer (II) forreactions to attach the cross-linking functional groups.

The grafting reaction is conveniently carried out in solution. Organicsolvents, such as toluene, are appropriate solvents for this graftingreaction. The grafting reaction can be carried out at atmosphericpressure and moderate temperatures, e.g. about 70° C. Higher or lowerpressures and temperatures can be used and such reaction conditions areconsidered within the scope of this invention.

The graft copolymer (II) is then reacted to attach azide cross-linkinggroups to the polymer chain to form an azide-functionalized polymer(III). For example, the grafted copolymer can be reacted with sodiumazide (NaN₃), as shown in FIG. 1, which reacts to displace the remainingchlorine atom from the chloromethyl group of the polymer with unitsderived from p-chloromethylstyrene. Suitable azide having thecharacteristic formula R(N₃)_(x) can be used in place of the sodiumazide, where x>zero (0) and R is a metal atom other than sodium, ahydrogen atom or an ammonium radical. A stoichiometric excess of theazide group (e.g., sodium azide) can be used to completely displace allthe chlorine atoms still present on the polymer chains and maximize thenumber of cross-linking moieties. Reaction conditions for attaching theazide groups can be similar to the previous reaction conditions forpolymerization and/or for grafting.

The resulting azide-functionalized graft copolymer (III) can bepurified, if desired, by a conventional method. One such method is toprecipitate the polymer (III) from solution, e.g., by adding to a “poor”solvent such as methanol, wash the precipitate, and dry the precipitateunder low temperatures (e.g., less than or equal to about 100° C.).

The azidomethyl groups serve as crosslinking moieties, which can beactivated either thermally (by heating) or photolytically (by exposureto ultraviolet (UV) light) to initiate crosslinking reactions of theazido functional groups and form crosslinked films ofpoly(styrene-g-ethylene oxide-r-para-azidomethylstyrene)(PS-g-PEO-g-p-azidomethylstyrene, or PS-r-PEO). The random polymers aredesigned to interact with both blocks of a self-assembling PEO-b-PSdiblock copolymer. The molecular weight (MW) of the random polymers isgenerally at about 30,000-50,000. An example of a random copolymer cancomprise about 20-80% PEO, about 80-20% PS (including grafted segments)and about 1-5% of azidomethylstyrene. Thin films of the resultingpolymers can be cast onto a substrate and fixed in place by thermally orphotolytically crosslinking the polymers to form a mat that is neutralwetting to PS and PEO and insoluble due to the crosslinking. The abilityto photolytically crosslink the random polymer allows for patterning ofthe polymer layer and registration of a PS-b-PEO film that is cast andannealed onto the substrate bearing the patterned mat.

Films of PS-b-PEO can be coated on a substrate bearing a layer (mat)composed of the crosslinked, neutral wetting random PS-r-PEO polymer ofthe invention and, upon annealing, the PS-b-PEO film will self-assembleinto morphologies that are oriented in response to the neutral wettingproperties of the crosslinked random polymer mat. For example, annealinga cylinder-phase PS-b-PEO film will orient the cylinders perpendicularto the substrate bearing the crosslinked polymer mat.

Processing conditions of embodiments of the invention use agraphoepitaxy technique utilizing the sidewalls of trenches asconstraints to induce orientation and registration of a film of aself-assembling diblock copolymer to form an ordered array patternregistered to the trench sidewalls. In some embodiments, selectiveremoval of one of the polymer domains can be performed to produce atemplate that can be used as a mask to etch features in an underlyingsubstrate.

Steps in a method for using the random graft PS-r-PEO copolymer of theinvention for fabricating a thin film from a self assembling (SA)PS-b-PEO block copolymer that defines nanometer-scale linear arraypatterns according to embodiments of the invention are illustrated inFIGS. 2-5.

In the described embodiment, a lamellar-phase PS-b-PEO block copolymerfilm is deposited onto a layer of the described random graft copolymerwhich provides a surface that is neutral wetting to both PS and PEO(exhibits non-preferential wetting toward PS and PEO). Upon annealing,the block copolymer film self-assembles to form a registered andlamellar array of alternating polymer-rich blocks (PS and PEO) thatextend the length of the trench and are oriented perpendicular to thetrench floor and parallel to the sidewalls.

To produce a lamellar polymer film within the trenches using alamellar-phase PS-b-PEO block copolymer, the surface of the sidewallsand edges of the trenches are preferential wetting by one block of thecopolymer and the trench floors are neutral wetting (equal affinity forboth blocks of the copolymer) to allow both blocks of the copolymermaterial to wet the floor of the trench. Entropic forces drive thewetting of a neutral wetting surface by both blocks, resulting in theformation of a layer of perpendicular lamellae across the width of eachtrench.

In an embodiment shown in FIGS. 2 and 2A, a layer 12 of the PS-r-PEOrandom copolymer of the invention has been formed on a substrate 10prior to forming the overlying material layer 14. The substrate 10 canbe composed, for example, of silicon, silicon oxide, silicon nitride,silicon oxynitride, silicon oxycarbide, among other materials.

A solution of the azidomethylstyrene-functionalized random copolymer(PS-r-PEO) in a solvent such as toluene, xylene, chloroform, andbenzene, among others, in which both monomers are soluble (e.g., about1% w/v solution) can be applied as a layer 12 onto the substrate 10 to athickness of about 1-100 nm, for example, by spin-coating. The randomcopolymer is cast to a minimum thickness such that the block PS-PEO castabove the random copolymer layer will entangle without contacting theunderlying substrate. The PS-r-PEO random copolymer can then be UVcrosslinked (e.g., 1-5 MW/cm̂2 exposure for about 15 seconds to about 30minutes) or thermally crosslinked (e.g., at about 170° C. for about 4hours), whereupon the copolymer forms a crosslinked mat on the surfaceof the substrate 10.

A material layer 14 can then be formed over the crosslinked PS-r-PEOrandom copolymer layer 12 and etched to form trenches 16 to expose thelayer 12 as a neutral wetting surface on the floor or bottom surface 18of the trench. The trenches 16 are structured with opposing sidewalls22, opposing ends 24, a width (w_(t)), a length (l_(t)) and a depth(D_(t)). Adjacent trenches are separated by a spacer (or crest) 20. Thetrenches can be formed using a lithographic tool having an exposuresystem capable of patterning at the scale of L_(o) (10-100 nm). Suchexposure systems include, for example, extreme ultraviolet (EUV)lithography, proximity X-rays and electron beam (e-beam) lithography, asknown and used in the art. Conventional photolithography can attain (atsmallest) about 58 nm features.

Referring now to FIG. 2B, in another embodiment, the material layer 14′can be formed on the substrate 10′ and etched to form the trenches 16′,and the neutral wetting random copolymer 12′ can then applied to thetrench floors 18′. For example, the random copolymer can be cast or spincoated as a blanket film over the material layer 14′ and into thetrenches, and then photo-exposed through a mask or reticle (not shown)to selectively crosslink the random copolymer only within the trenchesto form the neutral wetting layer 12′. Non-crosslinked random copolymermaterial outside the trenches (e.g., on the spacers 20′) can besubsequently removed.

A self-assembling (SA) lamellar-phase diblock copolymer material is thendeposited into the trenches and processed such that the copolymermaterial will self-assemble to form a lamellar film composed ofperpendicular-oriented, alternating polymer-rich blocks across the widthof the trench. In the illustrated example, the diblock copolymer is apoly(styrene-block-ethylene oxide) (PS-b-PEO) block copolymer.

The trench sidewalls, edges and floors influence the self-assembly ofthe polymer blocks and the structuring of the array of nanostructureswithin the trenches. The trench sidewalls 22 and ends 24 are structuredto be preferential wetting by one block of the block copolymer to induceregistration of lamellae as the polymer blocks self-assemble. Thematerial layer 14 defining the trench surfaces can be a material that isinherently preferential wetting to one of the blocks, or in otherembodiments, a layer of a preferential wetting material can be appliedonto the surfaces of the trenches. For example, in the use of a PS-b-PEOblock copolymer, in some embodiments, the material layer 14 can becomposed of silicon (with native oxide), oxide (e.g., silicon oxide,SiO_(x)) or other inorganic films, for example, which exhibitspreferential wetting toward the PEO block to result in the assembly of athin (e.g., ¼ pitch) interface layer of PEO and alternating PEO and PSlamellae (e.g., ½ pitch) within each trench in the use of alamellar-phase block copolymer material.

The boundary conditions of the trench sidewalls in both the x- andy-axis impose a structure wherein each trench contains “n” number oflamellae. Factors in forming a single array or layer of nanostructureswithin the trenches include the width and depth of the trench, theformulation of the block copolymer to achieve the desired pitch (L_(o)),and the thickness (t) of the copolymer film.

The trenches 16 are constructed with a width (w_(t)) such that a blockcopolymer (or blend) will self assemble upon annealing into a singlelayer of n lamellae spanning the width (w_(t)) of the trench, with thecenter-to-center distance of adjacent lamellae being at or about L_(o).In using a lamellar-phase block copolymer, the width (w_(t)) of thetrenches is a multiple of the inherent pitch value (L_(o)) of thepolymer being equal to or about nL_(o) (“n*L_(o)”), typically rangingfrom about n*10 to about n*100 nm (with n being the number of featuresor structures). The application and annealing of a lamellar-phase blockcopolymer material having an inherent pitch value of L_(o) in a trenchhaving a width (w_(t)) at or about L_(o) will result in the formation ofa single layer of n lamellae spanning the width and registered to thesidewalls for the length of the trench. In some embodiments, the trenchdimension is about 50-500 nm wide (w_(t)) and about 1,000-10,000 μm inlength (l_(t)), with a depth (D_(t)) of about 50-500 nm.

Referring now to FIGS. 3 and 3A, a layer 26 of a self-assemblinglamellar-phase PS-b-PEO diblock copolymer material having an inherentpitch at or about L_(o) (or a ternary blend of block copolymer andhomopolymers blended to have a pitch at or about L_(o)) is deposited,typically by spin casting (spin-coating) onto the floor 18 of thetrenches 16. The PS-b-PEO block copolymer material can be deposited, forexample, by spin casting a dilute solution (e.g., about 0.25-2 wt %solution) of the PS-b-PEO copolymer in an organic solvent such asdichloroethane (CH₂Cl₂), toluene or chloroform, for example.

The thickness (t₁) of the PS-b-PEO diblock copolymer layer 26 and at orabout the L_(o) value of the PS-b-PEO copolymer material such that thefilm layer will self assemble upon annealing to form a single layer oflamellae across the width (w_(t)) of the trench. In some embodiments,the trench depth (D_(t)) is greater than the film thickness (t₁). Atypical thickness (t₁) of a lamellar-phase PS-b-PEO block copolymer film26 is about ∀20% of the L_(o) value of the copolymer (e.g., about 10-100nm) to form alternating polymer-rich lamellar blocks having a width ofabout 0.5 L_(o) (e.g., 5-50 nm) within each trench. In the use of asolvent anneal, the film can be much thicker than L_(o), e.g., up toabout +1000% of the L_(o) value. The thickness of the film 26 can bemeasured, for example, by ellipsometry techniques. As shown, a thin film26 of the block copolymer material can be deposited onto the spacers 20of the material layer 14; this film will form a monolayer of lamellae ina parallel orientation with no apparent structure from a top-down(etching) perspective.

The volume fractions of the two blocks (AB) of the PS-b-PEO diblockcopolymer are generally at a ratio between about 50:50 and 60:40. Anexample of a lamellae-forming symmetric diblock copolymer is PS-b-PEOwith a weight ratio of about 50:50 (PS:PEO) and total molecular weight(M_(n)) of about 19 kg/mol. Although PS-b-PEO diblock copolymers areused in the illustrative embodiments of this disclosure, triblock ormultiblock copolymers can also be used.

The PS-b-PEO block copolymer material can also be formulated as a binaryor ternary blend comprising a PS-b-PEO block copolymer and one or morehomopolymers (i.e., polystyrene (PS) and polyethylene oxide (PEO) toproduce blends that swell the size of the polymer domains and increasethe L_(o) value of the polymer. The volume fraction of the homopolymerscan range from 0 to about 40%. An example of a ternary diblock copolymerblend is a PS-b-PEO/PS/PEO blend. The L_(o) value of the polymer canalso be modified by adjusting the molecular weight of the blockcopolymer, e.g., for lamellae, L_(o)˜(MW)^(2/3).

Referring now to FIGS. 4 and 4A, the PS-b-PEO block copolymer film 26 isthen annealed to cause the polymer blocks to phase separate and selfassemble according to the preferential and neutral wetting of the trenchsurfaces 18, 22, 24 to form a self-assembled polymer film 28.

In some embodiments, the film 26 can be solvent annealed. In a solventanneal, the film is swollen by exposure to a vapor of a “good” solventfor both blocks and then removal of the vapor. Vapors of a solvent suchas benzene, chloroform or a chloroform/octane mixture, for example, canbe exposed to the film 26 to slowly swell both blocks (PS, PEO) of thefilm. The solvent and solvent vapors are then allowed to slowlyevaporate to dry the film, resulting in self-assembled lamellar domainsoriented perpendicular to the substrate 10. The presence of the neutralwetting PS-r-PEO random block copolymer film 12 over the surface of thesubstrate 10 on the floors 18 of the trenches allows the self-assemblingpolymer domains to extend completely from the film-air interface to thesubstrate surface (trench floors 18).

The PS-PEO copolymer film can also be thermally annealed at theannealing temperature (e.g., about 150-250° C.) in an atmosphere that issaturated (but not supersaturated) with a solvent in which both blocksare soluble. The solvent-saturated vapor maintains a neutral airinterface in conjunction with the surface interface with the neutralwetting random copolymer layer 12. The existence of both neutral wettingair and surface interfaces induces the formation of perpendicularfeatures throughout the film by thermal annealing over regions coatedwith the neutral-wetting random copolymer of the invention.

The constraints provided by the width (w_(t)) of the trenches and thecharacter of the copolymer composition combined with preferential orneutral wetting surfaces within the trenches result, upon annealing, ina single layer of n lamellae across the width (w_(t)) of the trench. Thenumber “n” or pitches of lamellar blocks within a trench is according tothe width (w_(t)) of the trench and the molecular weight (MW) of thePS-r-PEO block copolymer. As shown in FIG. 4A, lamellar-phase blockcopolymer material will, upon annealing, self assemble into a film 28composed of perpendicular-oriented, alternating polymer-rich blocks 30,32 spanning the width (w_(t)) of the trench 16 at an average pitch valueat or about L_(o). For example, depositing and annealing an about 50:50PS:PEO block copolymer film (e.g., M_(n)=19 kg/mol; L_(o)=19 mm) in anabout 250 nm wide trench will subdivide the trench into about 12lamellar pitches. The resulting morphology of the annealed film 28(i.e., perpendicular orientation of lamellae) can be examined, forexample, using atomic force microscopy (AFM), transmission electronmicroscopy (TEM), scanning electron microscopy (SEM).

Optionally, the annealed and ordered film 28 can then be treated tocrosslink the polymer segments to fix and enhance the strength of theself-assembled polymer blocks 30, 32 within the trench 16 (e.g., tocrosslink the PS segments). The polymers can be structured to inherentlycrosslink (e.g., upon exposure to ultraviolet (UV) radiation, includingdeep ultraviolet (DUV) radiation), or one or both of the polymer blocksof the copolymer material can be formulated to contain a crosslinkingagent. Optionally, the material 26 outside the trench (e.g., on spacer20) can then be removed as shown. If the material layer 12 is a hardmask (e.g., not etched) relative to etching of substrate to at a laterstep, the removal of material 26 outside the trench is not necessary.

For example, in one embodiment, the trench regions can be selectivelyexposed through a reticle (not shown) to crosslink only theself-assembled film 28 within the trench 16, and a wash can then beapplied with an appropriate solvent (e.g., toluene) to remove thenon-crosslinked portions of the film 28 (e.g., material 26 on the spacer20) leaving the registered self-assembled film within the trench andexposing the surface of material layer 14 above/outside the trench(e.g., the spacer 20). In another embodiment, the annealed film 28 canbe crosslinked globally, a photoresist layer can be applied to patternand expose the areas of the film outside the trench regions (e.g., overthe spacers 20), and the exposed portions of the film can be removed,for example by an oxygen (O₂) plasma treatment. In other embodiments,the spacers 20 are narrow in width, for example, a width (w_(s)) of oneof the copolymer domains (e.g., about L_(o)) such that the material 26on the spacers is minimal and no removal is required.

Referring now to FIGS. 5 and 5A, one of the block components can beselectively removed to produce a thin film 34 that can be used, forexample, as a lithographic template or mask to pattern the underlyingsubstrate 10 in a semiconductor processing to define regular patterns inthe nanometer size range (i.e., about 10-100 nm).

For example, selective removal of PEO domains 30 will result in openings(slits) 36 separated by vertically oriented walls composed of PS domains32, and the neutral wetting PS-r-PEO random copolymer layer 12 exposedon the trench floor 18. Removal of the water-soluble PEO phase domainscan be performed, for example, by exposure of the film to aqueoushydroiodic acid or exposure to water alone, which will draw PEO to thesurface without cleaving the bonds to the PS domains. In embodiments inwhich the PS-b-PEO block copolymer includes an acid-cleavable linker(e.g., trityl alcohol linker) positioned between the polymer blocks,exposure of the film to an aqueous acid (e.g., trifluoroacetic acid) orto an acid vapor can be performed to cleave the polymer into PEO and PSfragments (S. Yurt et al., “Scission of Diblock Copolymers into TheirConstituent Blocks,” Macromolecules 2006, 39, 1670-1672). Rinsing withwater can then be performed to remove the cleaved PEO domains. In otherembodiments, exposure to water to draw the PEO domains to the surfacefollowed by a brief oxygen (O₂) plasma etch can also be performed toremove the PEO domains on the surface of the film to form voids andreveal underlying PS domains.

In embodiments in which the PS phase domains 32 are removed, theopenings (slits) are separated by walls composed of the PEO domains 30.

In some embodiments, the resulting film 34 has a corrugated surface thatdefines a linear pattern of fine, nanometer-scale, parallel slits(openings) 36 about 5-50 nm wide and several microns in length (e.g.,about 10-4000 μm), the individual slits separated by walls (e.g., ofblock 32) about 5-50 nm wide, providing an aspect ratio ranging fromabout 1:2 to about 1:20. For example, removal of the PEO domains affordsa PS mask of sublithographic dimensions, for example, a pitch of about35 nm (17.5 nm PS domain). A smaller pitch can be dialed in by usinglower molecular weight diblock copolymers.

The films can be used, for example, as a lithographic template or etchmask to pattern (arrows ↓↓) the underlying substrate 10, for example, bya non-selective RIE etching process, to delineate a series of channelsor grooves 38, shown in phantom in FIG. 5A, extending to an active areaor element 40 in the substrate or an underlayer. In some embodiments,the channels 38 can then be filled with a material 42 as illustrated inFIG. 5B, for example, a conductive material (e.g., metal) to formnanowire channel arrays for transistor channels, semiconductorcapacitors, and other structures, or a dielectric material to separateactive areas (e.g., substrate 10). Further processing can then beperformed as desired.

The films provide linear arrays having long range ordering andregistration for a wide field of coverage for templating a substrate.The films are useful as etch masks for producing close pitched nanoscalechannel and grooves that are several microns in length, for producingfeatures such as floating gates for NAND flash with nanoscaledimensions. By comparison, photolithography techniques are unable toproduce channels much below 60 nm wide without high expense. Resolutioncan exceed other techniques such as conventional photolithography, whilefabrication costs utilizing methods of the disclosure are far less thanelectron beam (E-beam) or EUV photolithographies which have comparableresolution.

A method according to another embodiment of the invention for formingthin films of a cylindrical-phase, self-assembling PS-b-PEO blockcopolymer that define an array of perpendicularly-oriented cylinders ina polymer matrix is illustrated with reference to FIGS. 6-8. Thedescribed embodiment utilizes topographical features, the sidewalls andends of trenches, as constraints to induce orientation and registrationof cylindrical copolymer domains to achieve an array of hexagonal-packedand perpendicularly-oriented cylinders within a polymer matrixregistered to the trench sidewalls.

As described with reference to FIGS. 2 and 2A, a trench 16″ can beetched in a material layer 14″ to expose a neutral wetting surface 12″(composed of the PS-r-PEO random copolymer of the invention on anunderlying substrate 10″. The width (w_(t)) of the trench 16″ is at orabout L_(o)*cos(π/6) or L_(o)*0.866, which defines the number of rows ofcylinders, and the trench length (l_(t)) is at or about mL_(o), whichdefines the number of cylinders per row. The ends 24″ of the trenchesare angled to the sidewalls 22 as shown in FIG. 6, for example, at anabout 60° angle, and in some embodiments can be slightly rounded.

The trenches are also structured such that the trench floor 18″ isneutral wetting to both blocks of the PS-b-PEO block copolymer material,and the sidewalls 22″ and ends 24″ are preferential wetting by theminority block of the copolymer. Entropic forces drive the wetting of aneutral-wetting surface by both blocks, resulting in a perpendicularorientation of the self-assembled cylinders. As previously described, aneutral wetting layer 12″ can be provided, for example, by applying thePS-r-PEO random copolymer of the invention onto the surface of thesubstrate 10″ (e.g., spin-coating) and crosslinking the copolymer layerbefore forming the material layer 14″ and the trenches 16″ to expose theneutral wetting layer 12″ forming the trench floors 18″.

As previously described, sidewalls 22″ and ends 24″ that arepreferential wetting toward the PEO block of a PS-b-PEO diblockcopolymer can be provided by a material layer 14″ composed, for example,of oxide. Upon annealing, the PEO block of the PS-b-PEO copolymer layerwill segregate to the sidewalls and ends of the trench to form a wettinglayer (30 a″ in FIGS. 6 and 6A).

With reference to FIGS. 3 and 3A, a layer 26″ of a cylindrical-phasePS-b-PEO diblock copolymer material having an inherent pitch at or aboutL_(o) (or blend with homopolymers) is deposited onto the neutral wettingPS-r-PEO random copolymer layer 12″ on the floor 18″ of the trench 16″to a thickness (t₁) of less than or about equal to the L_(o) value ofthe copolymer material to up to about 1.5×L_(o) (or larger if annealedby solvent annealing) such that the copolymer film layer will selfassemble upon annealing to form a hexagonal array of perpendicularcylindrical domains having a diameter of about 0.5 L_(o) (e.g., about 20nm) in the middle of a polymer matrix within each trench (e.g., with theadjacent cylindrical domains having a center-to-center distance of at orabout L_(o) (e.g., about 35-40 nm).

The PS-b-PEO block copolymer film 26″ is then annealed, resulting in aself-assembled lamellar film 28″ as shown in FIGS. 6 and 6A. Thecharacter of the cylindrical-phase block copolymer composition 26″combined with a neutral wetting trench floor 18″ and preferentialwetting sidewalls 22″ and ends 24″, and constraints provided by thewidth (w_(t)) of trench 16″ results, upon annealing, in a hexagonalarray of perpendicularly-oriented cylindrical domains 30″ of the minorpolymer block (i.e., like domains) (e.g., PEO) within a matrix 32″ ofthe major polymer block (e.g., PS). A thin layer 30 a″ of the minorpolymer block (e.g., PEO) wets the sidewalls 18″. The hexagonal arraycontains n single rows of cylinders according to the width (w_(t)) ofthe trench with the cylinders 30″ in each row being offset from thecylinders in the adjacent rows. Each row contains a number of cylinders,generally m cylinders, which number can vary according to the length(l_(t)) of the trench and the shape of the trench end (e.g., rounded,angled, etc.) with some rows having greater or less than m cylinders.The cylinders 38 a″ are generally spaced apart at a pitch distance (p₁)at or about L_(o) between each cylinder in the same row and an adjacentrow (center-to-center distance), and at a pitch distance (p₂) at orabout L_(o)*cos(π/6) or 0.866 L_(o) being the distance between twoparallel lines where one line bisects the cylinders in a given row andthe other line bisects the cylinders in an adjacent row.

Optionally, the annealed film 28″ can then treated to crosslink thepolymer segments (e.g., to crosslink the PS matrix 32″). As previouslydescribed, the polymers can be structured to inherently crosslink, orone or both of the polymer blocks of the copolymer material can beformulated to contain a crosslinking agent. The polymer materialremaining on the spacers 20″ can then be optionally removed aspreviously described.

One of the block components can then be selectively removed from theself-assembled 28″ film. In one embodiment shown in FIGS. 7 and 7A, thecylindrical domains 30″ can be removed to produce a film 34 a″ composedof the matrix 32″ with a hexagonal array of cylindrical openings 36″. Inanother embodiment shown in FIGS. 8-8B, the matrix 32″ can be removed toproduce a film 34 b″ composed of a hexagonal array of cylinders 30″ onthe substrate 10″. The resulting films 34 a″, 34 b″ can be used, forexample, as a lithographic template or mask to pattern the underlyingsubstrate 10″ in a semiconductor processing to define regular patternsin the nanometer size range (i.e., about 5-50 nm).

For example, referring to FIGS. 7 and 7A, selective removal of the minorblock cylinders 30″ (e.g., PEO) will result in a film 34 a″ composed ofa hexagonal array of openings 36″ within the matrix 32″ of the majorblock (e.g., PS), the openings having a diameter of about 5-50 nm and anaspect ratio generally at least about 1:2 and ranging from about 1:2 toabout 1:20. The film 34 a″ can be used as an etch mask to pattern(arrows ↓↓) the underlying substrate 10″ to form an array of openings38″ (shown in phantom in FIG. 7A) to an active area or element 40″ inthe substrate 10″. Further processing can then be performed as desired,for example, the removal of the residual matrix 32″ (e.g., PS) andfilling of the openings 38″ in substrate 10″ as shown in FIG. 7B, with amaterial 42″ such as a metal or conductive alloy such as Cu, Al, W, Si,and Ti₃N₄, among others, to form contacts, for example, to an underlyingactive area or conductive line 40″, or with a metal-insulator-metalstack to form capacitors with an insulating material such as SiO₂,Al₂O₃, HfO₂, ZrO₂, SrTiO₃, among other dielectrics.

In another embodiment illustrated in FIGS. 8 and 8A, the selectiveremoval of the major block matrix 32″ (e.g., PEO) will provide a film 34b″ composed of a hexagonal array of the minor block cylinders 30″ (e.g.,PS) on the substrate 10″. Such an embodiment would require a majorityPEO block copolymer and sidewalls composed of a material that isselectively PS-wetting (e.g., a gold sidewall or PS-grafted to thesidewall material). The film 34 b″ composed of cylinders 30″ can be usedas an etch mask (arrows ↓↓) to etch a patterned opening 38″ in theunderlying substrate 10″ (shown in phantom in FIG. 8A) with thesubstrate 10″ etched to form cylinders masked by the cylindricalelements 30″ of the film 34 b″. Further processing can then beconducted, for example, the removal of the residual polymer mask 34 b″(i.e., cylinders 30″) and the deposition of a material 42″ distinct fromsubstrate 10″ into the opening 36″ to provide a differential surface, asillustrated in FIG. 8B. For example, an opening 36″ in a siliconsubstrate 10″ can be filled with a dielectric material such as SiO₂,with the cylinders of the residual substrate 10″ (e.g., of silicon)providing contacts to an underlying active area or metal lines 40″.

In an embodiment of a method to produce a one-dimensional (1-D) array ofperpendicularly-oriented cylinders as illustrated in FIGS. 9-11, theforegoing process for forming a hexagonal array of cylinders with acylindrical-phase PS-b-PEO block copolymer can be modified by utilizingthe trench sidewalls and ends as constraints to induce orientation andregistration of cylindrical copolymer domains in a single row parallelto the trench sidewalls.

Referring to FIGS. 2 and 2A, in embodiments to provide a single row ofcylinders within a polymer matrix, a trench 16″′ is structured to have awidth (w_(t)) that is at or about 1.5-1.75*the L_(o) value of the blockcopolymer material. The material layer 14″′ (e.g., oxide) exposed on thesidewalls 22″ and ends 24″′ is preferential wetting by the minorityblock (e.g., the PEO block) of the PS-b-PEO diblock copolymer, and thesubstrate 10″′ (e.g., silicon) bear a layer 12″′ of the PS-r-PEO randomcopolymer of the invention, which is exposed at the trench floors 18″′and neutral wetting to both blocks of the PS-b-PEO copolymer material.

A cylindrical-phase PS-b-PEO diblock copolymer material 26″′ (or blendwith homopolymers) having an inherent pitch at or about L_(o) can bedeposited onto the PS-r-PEO layer 12″′ on the trench floor 18″′ to athickness (t₁) of less than or about equal to the L_(o) value of thecopolymer material to up to about 1.5×L_(o) (as shown in FIGS. 3 and3A). The block copolymer film 26″′ is then annealed, whereupon thecopolymer film layer will self assemble to form a film 28″′, asillustrated in FIGS. 9 and 9A. The constraints provided by the width(w_(t)) of trench 16″′ and the character of the block copolymercomposition 26″′ combined with a neutral wetting trench floor 18″′ andpreferential wetting sidewalls 22″′ and ends 24″′ results in aone-dimensional (1-D) array or single row of perpendicularly-orientedcylindrical domains 30″′ of the minority polymer block (e.g., PEO)within a matrix 32″′ of the major polymer block (e.g., PS), with theminority block segregating to the sidewalls 18″′ of the trench to form awetting layer 30 a″′. In some embodiments, the cylinders have a diameterat or about 0.5 L_(o) (e.g., about 20 nm), the number n of cylinders inthe row is according to the length of the trench, and thecenter-to-center distance (pitch distance) (p) between each like domain(cylinder) is at or about L_(o) (e.g., about 40 nm). Optionally, theannealed cylindrical-phase film 28′″ can be treated to crosslink thepolymer segments (e.g., the PS matrix 32″′).

Selective removal of one of the block components can then be performedto produce, for example, a film that can be used as a mask to etch theunderlying substrate 10″′. For example, referring to FIGS. 10 and 10A,selective removal of the minor block cylinders 30″′ (e.g., PEO) willresult in a film 34 a′41 composed of a 1-D array of cylindrical openings36′″ within the matrix 32″′ of the major block (e.g., PS), the openingshaving a diameter of about 5-50 nm and an aspect ratio of about 1:2 toabout 1:20. The film 34 a′″ can be used as an etch mask to pattern(arrows ↓↓) the underlying substrate 10″′ to form an array of openings38″′ (shown in phantom in FIG. 10A) extending to an active area orelement 40″′. The residual film 34 a″′ can then be removed and theopenings 38′″ in the substrate 10″′ can be filled as shown in FIG. 10Bwith a material 42″′, for example, a metal or conductive alloy toprovide a 1-D array of contacts to an underlying active area or linecontact 40″′, for example, or with metal-insulator-metal stack to formcapacitors.

In another embodiment depicted in FIGS. 11-11B, the selective removal ofthe major block matrix component 32′″ (e.g., PEO) will provide a film 34b′″ composed of a 1-D array of the minor block cylinders 30″′ (e.g.,PS). The film 34 b″′ can be used as a mask or template in an etchprocess (arrows 11) to form a patterned opening 38″′ (shown in phantomin FIG. 11A) in the underlying substrate 10″′, with the masked substrate10″′ etched to form cylinders. The residual polymer mask 34 b″′(cylinders 30″′) can then be removed and a material 42 b″′ such as adielectric material (e.g., oxide) that is distinct from the substrate10″′ (e.g., silicon) can be deposited to fill the opening 36″ to providea differential surface to the substrate 10″ cylinders, which can providecontacts to an underlying active area or metal line 40″′, for example.

In another embodiment of the invention, graphoepitaxy (topographicfeatures, e.g., sidewalls, ends, etc.) is used to influence theformation of arrays in one dimension, and the trench floors provide awetting pattern that can be used to chemically control formation of thearrays in a second dimension. A layer 12″″ of the PS-r-PEO randomcopolymer layer of the invention is formed on a substrate 10″″, andcrosslinked in select regions or sections 12 a″″, for example, byphoto-exposure (arrows ↓↓) through a reticle or a mask 44″″ as shown inFIGS. 12 and 12A, or through a patterned resist layer 46″″ as depictedin FIGS. 13 and 13A (which is subsequently removed). The non-crosslinkedregions 12 b″″ of the PS-r-PEO random copolymer layer 12″″ can beremoved, for example, by wet processing using an appropriate solvent toexpose the underlying substrate 10″″, resulting in a pattern of discreteregions or sections of the crosslinked random copolymer layer 12 a″″(neutral wetting) and sections of the exposed substrate 10″″(preferential wetting) on the trench floor 18″″, as shown in FIGS. 14and 14A.

As depicted in FIGS. 15-15B, a material layer 14″″ can then be formedand trenches 16″″ etched to expose the crosslinked sections 12 a″″ ofthe PS-r-PEO random copolymer layer and sections of the exposedsubstrate 10″″ on the trench floors 18″″ as a series of stripes orientedperpendicular to the trench sidewalls 22″″. The trench floors 18″″ arethus defined by alternating preferential wetting sections (substrate10″″) and neutral wetting sections (a mat of the crosslinked PS-r-PEOrandom copolymer 12 a″″). In some embodiments, each of the sections canhave a width (w_(r1)) at or about L_(o), and in other embodiments, theneutral wetting (PS-r-PEO) sections 12 a″″ can have a width (w_(r2)) ator about nL_(o) and the preferential wetting (substrate) sections 10″″ awidth at or about L_(o). The trench sidewalls 22″″ and edges 24″″ (e.g.,of oxide) are preferential wetting to the minority block (e.g., PEO) ofthe PS-b-PEO diblock copolymer.

Referring now to FIGS. 16 and 16A, a cylindrical-phase PS-b-PEO blockcopolymer film 26″″ (e.g., having a pitch L_(o)) is cast or spin coatedinto the trenches 16″″ to a film thickness (t) of about L_(o), and thenthermally annealed as previously described. The differing wettingpatterns on the trench floor 18″″ imposes ordering on the PS-b-PEO blockcopolymer film 26″″ as it is annealed, resulting in a 1-D array ofalternating perpendicular-oriented cylinders 30 a″″ andparallel-oriented cylinders 30 c″″ for the length (nL_(o)) of eachtrench 16″″, as shown in FIGS. 17-17B. In some embodiments, the filmstructure is composed of a series of n perpendicular cylinders 30 b″″for the width (w₁) of each neutral wetting PS-r-PEO polymer section 12a″″ on either side of a region of a single parallel-orientedhalf-cylinder 30 c″″ for the width (w₂) of each preferential wettingsection (exposed substrate 10″″).

Optionally, the annealed film 28″″ can then be treated to crosslink thepolymer segments (e.g., the PS matrix 32″″) as previously described.Material outside the trenches can be optionally removed, for example,from the spacers 20″″.

Selective removal of one of the polymer domains (i.e., cylinders ormatrix) can then be performed to produce a template for use inpatterning the substrate 10″″. For example, as shown in FIGS. 18-18B,selective removal of the cylindrical domains 30 b″″, 30 c″″ (e.g., ofPEO) will produce an array of openings 36 a″″, 36 b″″ within a polymermatrix 32″″ (e.g., of PS), which will vary according to the orientationof the cylindrical domains within the trenches. Only openings 36 a″″will extend to the trench floor 18″″, with majority block matrixcomponent 32″″ (e.g., PS) remaining underneath the half-cylinderopenings 36 b″″.

As shown in FIGS. 19A and 19B, the resulting film 34″″ can be then usedin patterning (arrows ↓↓) substrate 10″″ to form a configuration ofcylindrical openings 38″″ (shown in phantom) extending to an active areaor element 40″″. The film 34″″ can then be removed and the openings 38″″can be filled with a material 42″″ (e.g., metal, conductive alloy) asshown in FIGS. 20-20B to provide a series of perpendicular contacts 42″″to underlying active areas or elements (e.g., line contact) 40″″, withadditional processing as desired.

In yet another embodiment illustrated in FIGS. 21-21B, selective removalof the major block matrix component 32″″(e.g., PEO) will provide a film34″″ composed of an array of the minor block cylinders 30 b″″ (e.g., PS)on the substrate 10″″, which can be used to etch (arrows ↓↓) openings38″″ in substrate 10″″ (shown in phantom), with the masked portions ofthe substrate 10″″ etched in the form of cylinders. The residual mask34″″ (cylinders 30″″) can be removed and, as shown in FIGS. 22-22B, amaterial 42″″ distinct from the substrate 10″″ (e.g., silicon) such as adielectric material (e.g., oxide) can be deposited to fill the opening36″″ as a differential material than the substrate 10″″ cylinders, whichcan provide, for example, contacts to an underlying active area or metalline 40″″.

Embodiments of the invention provide ordered and registered elements ona nanometer scale that can be prepared more inexpensively than byelectron beam lithography or EUV photolithography. The feature sizesproduced and accessible by this invention cannot be prepared byconventional photolithography.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement which is calculated to achieve the same purpose maybe substituted for the specific embodiments shown. This application isintended to cover any adaptations or variations that operate accordingto the principles of the invention as described. Therefore, it isintended that this invention be limited only by the claims and theequivalents thereof. The disclosures of patents, references andpublications cited in the application are incorporated by referenceherein.

1. A method for fabricating a film comprising nanoscale microstructures, comprising: forming a film comprising a poly(styrene-b-ethylene oxide) block copolymer within a trench in a substrate, the trench having sidewalls, a width, a length, and a floor bearing a crosslinked material of an azido-functionalized random poly(styrene-r-ethylene oxide) graft copolymer; and annealing the film comprising the poly(styrene-b-ethylene oxide) block copolymer to form a polymer material comprising self-assembled polymer domains registered to the sidewalls and extending the length of the trench.
 2. The method of claim 1, further comprising crosslinking the self-assembled polymer domains of the annealed polymer material.
 3. A method for fabricating a film comprising nanoscale microstructures, comprising: forming a solution comprising an azido-functionalized random graft copolymer by: reacting a reaction mixture comprising p-chloromethylstyrene monomers to form a p-chloromethylstyrene homopolymer comprising chloromethyl moieties and repeating units derived from p-chloromethylstyrene; reacting the p-chloromethylstyrene homopolymer with one or more oligomers or polymers of poly(ethylene oxide) to form a graft copolymer comprising chloromethyl moieties, wherein the poly(ethylene oxide) has only one nucleophilic end; and reacting the graft copolymer with an azide compound to displace chlorine atoms of the chloromethyl moieties to form azidomethyl moieties on the graft copolymer, wherein the azide compound is selected from the group consisting of sodium azide and R(N₃)_(x), where R is a metal atom other than sodium, a hydrogen atom or an ammonium radical, and x is greater than zero; applying the solution comprising the azido-functionalized random graft copolymer to a floor of at least one trench in a substrate to form a random graft copolymer material; crosslinking at least a portion of the random graft copolymer material; forming a self-assembling block copolymer on the random graft copolymer material; and annealing the self-assembling block copolymer to form a material comprising self-assembled polymer domains.
 4. (canceled)
 5. The method of claim 3, wherein the at least one trench in the substrate comprises sidewalls that are preferentially wetting to one block of the self-assembling block copolymer.
 6. The method of claim 3, wherein the self-assembled polymer domains are oriented perpendicular to the floor of the at least one trench.
 7. The method of claim 3, wherein the self-assembling block copolymer is a lamellar-phase block copolymer.
 8. The method of claim 3, wherein the self-assembling block copolymer is a cylindrical-phase block copolymer.
 9. The method of claim 3, wherein the random graft copolymer material is neutral wetting to both blocks of the self-assembling block copolymer.
 10. The method of claim 3, wherein the self-assembling block copolymer has a thickness of about an L_(o) value of the self-assembling block copolymer.
 11. The method of claim 3, wherein crosslinking at least a portion of the random graft copolymer material comprises: masking one or more portions of the random graft copolymer material; crosslinking the unmasked portions of the random graft copolymer material; and selectively removing non-crosslinked portions of the random graft copolymer material to expose portions of the substrate.
 12. The method of claim 11, wherein the self-assembling block copolymer is a cylindrical-phase block copolymer, and the self-assembled polymer domains comprise perpendicular-oriented cylindrical polymer domains on the portions of the crosslinked random graft copolymer material and parallel-oriented half-cylindrical domains on the exposed portions of the substrate.
 13. The method of claim 3, wherein crosslinking at least a portion of the random graft copolymer material comprises: crosslinking the random graft copolymer material; masking one or more portions of the crosslinked random graft copolymer material; and removing unmasked portions of the crosslinked random graft copolymer material to expose the substrate on the floor of the at least one trench.
 14. A method for fabricating a film comprising nanoscale microstructures, comprising: forming a solution comprising an azido-functionalized random graft copolymer by: reacting a reaction mixture comprising p-chloromethylstyrene and styrene to form polymer chains comprising chloromethyl moieties and repeating units derived from p-chloromethylstyrene and styrene, wherein the reaction mixture comprises p-chloromethylstyrene in a molecular amount greater than a molecular amount of the styrene; reacting the polymer chains with one or more oligomers or polymers of poly(ethylene oxide) to form a graft copolymer comprising chloromethyl moieties, wherein the poly(ethylene oxide) has only one nucleophilic end; and reacting the graft copolymer comprising chloromethyl moieties with an azide compound to displace chlorine atoms of the chloromethyl moieties to form azidomethyl moieties on the graft copolymer; applying the solution comprising the azido-functionalized random graft copolymer to a floor of at least one trench in a substrate to form a random graft copolymer material; crosslinking the random graft copolymer material; forming a self-assembling block copolymer on the random graft copolymer material; and annealing the self-assembling block copolymer to form a material comprising self-assembled polymer domains.
 15. The method of claim 14, further comprising, after forming the random graft copolymer material: masking one or more portions of the random graft copolymer material; crosslinking exposed portions of the random graft copolymer material; and selectively removing non-crosslinked portions of the random graft copolymer material to expose portions of the substrate on the floor of the at least one trench.
 16. The method of claim 15, wherein the self-assembling block copolymer is a cylindrical-phase block copolymer, and the self-assembled polymer domains comprise perpendicular-oriented cylindrical domains on the crosslinked random graft copolymer material and parallel-oriented half cylindrical domains on the exposed substrate.
 17. The method of claim 14, further comprising, after crosslinking the random graft copolymer material: masking one or more portions of the crosslinked random graft copolymer material; and removing exposed portions of the crosslinked random graft copolymer material to expose the substrate on the floor of the at least one trench.
 18. A polymeric film on a substrate, comprising a self-assembled poly(styrene-b-ethylene oxide) block copolymer film within at least one trench in a substrate, the self-assembled poly(styrene-b-ethylene oxide) block copolymer film comprising self-assembled domains, the at least one trench having sidewalls, a width, a length, and a floor bearing a crosslinked material of an azido-functionalized random poly(styrene-r-ethylene oxide) graft copolymer, wherein the self-assembled domains extend from and interface with air and the substrate at the floor.
 19. The polymeric film of claim 18, wherein the self-assembled domains comprise perpendicularly oriented, alternating lamellar polymer domains.
 20. The polymeric film of claim 18, wherein the self-assembled domains comprise perpendicularly oriented cylinders.
 21. The polymeric film of claim 18, wherein the perpendicularly oriented cylinders extend the length of the trench in a single array.
 22. The film of claim 18, wherein the perpendicularly oriented cylinders are in a hexagonal array.
 23. A template, comprising a self-assembled poly(styrene-b-ethylene oxide) block copolymer film within a trench having sidewalls, a width, a length, and a floor bearing a crosslinked material of an azido-functionalized random poly(styrene-r-ethylene oxide) graft copolymer, the self-assembled poly(styrene-b-ethylene oxide) block copolymer film comprising a plurality of linear openings exposing the floor of the trench and separated by perpendicularly-oriented, lamellar polymer domains at a pitch distance of about L_(o) extending the length of the trench about parallel to the sidewalls, wherein the perpendicularly-oriented, lamellar polymer domains extend from and interface with air and the substrate at the floor of the trench.
 24. The template of claim 23, wherein the linear openings are about 5 nm to 60 nm wide.
 25. A template, comprising a self-assembled poly(styrene-b-ethylene oxide) block copolymer film within a trench having sidewalls, a width, a length, and a floor bearing a crosslinked material of an azido-functionalized random poly(styrene-r-ethylene oxide) graft copolymer, the self-assembled poly(styrene-b-ethylene oxide) block copolymer film comprising a plurality of perpendicularly-oriented cylindrical openings within a polymer matrix, the perpendicularly-oriented cylindrical openings exposing the floor of the trench and at a pitch distance of about L_(o), wherein the polymer matrix extend from and interface with air and the substrate at the floor of the trench.
 26. A template, comprising a self-assembled poly(styrene-b-ethylene oxide) block copolymer film within a trench having sidewalls, a width, a length, and a floor bearing a crosslinked material of an azido-functionalized random poly(styrene-r-ethylene oxide) graft copolymer, the self-assembled poly(styrene-b-ethylene oxide) block copolymer film comprising a plurality of perpendicularly-oriented cylinders supported by the floor of the trench and at a pitch distance of about L_(o), the floor of the trench exposed between the perpendicularly-oriented cylinders, the perpendicularly-oriented cylinders extending from and interfacing with air and the substrate at the floor of the trench. 